PSLE
George had pink notebooks and blue notebooks for sale. He sold 360 pink notebooks. 70% of the notebooks sold were blue.

1. How many pink notebooks and blue notebooks did George sell altogether?
2. He sold 50% of his notebooks. 70% of the notebooks left unsold were pink. How many blue notebooks did George have at first?

	Pink	Blue	Total	Total in percent
Before	10 u	10 u	20 u	100%
Change	- 30% - 3 u	- 70% - 7 u	- 100% - 10 u	- 50%
After	70% 7 u	30% 3 u	100% 10 u	50%

70% = ⁷⁰₁₀₀ = ⁷₁₀

Total number of notebooks sold = 10 u
Number of blue notebooks sold = 7 u

Number of pink notebooks sold
= 10 u - 7 u
= 3 u

3 u = 360

1 u = 360 ÷ 3 = 120

Total number of notebooks sold
= 10 u
= 10 x 120
= 1200

(b)
Percent of the notebooks left unsold
= 100% - 50%
= 50%

50% of the notebooks that were sold = 10 u
50% of the notebooks that were left unsold = 10 u

Percent of the notebooks left unsold that were pink = 70%
Percent of the notebooks left unsold that were blue = 100% - 70% = 30%

Number of the notebooks left unsold that were blue
= 30% x 10 u
= ³⁰₁₀₀ x 10 u
= 3 u

Number of blue notebooks that George had at first
= 3 u + 7 u
= 10 u
= 10 x 120
= 1200

Answer(s): (a) 1200; (b) 1200